<!DOCTYPE html>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>简单拖曵原理实例</title>
    <style type="text/css">
        #drag{width:400px;height:300px;background:url(http://upload.yxgz.cn/uploadfile/2009/0513/20090513052611873.jpg);cursor:move;position:absolute;top:100px;left:100px;border:solid 1px #ccc;}
        h2{color:#fff;background: none repeat scroll 0 0 rgba(16, 90, 31, 0.7);color:#FFFFFF;height:40px;line-height:40px;margin:0;}
    </style>
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js" type="text/javascript"></script>
    <script type="text/javascript">
        $(function(){
            /*--------------拖曳效果----------------
            *原理：标记拖曳状态dragging ,坐标位置iX, iY
            *         mousedown:fn(){dragging = true, 记录起始坐标位置，设置鼠标捕获}
            *         mouseover:fn(){判断如果dragging = true, 则当前坐标位置 - 记录起始坐标位置，绝对定位的元素获得差值}
            *         mouseup:fn(){dragging = false, 释放鼠标捕获，防止冒泡}
            */
            var dragging = false;
            var iX, iY;
            $("#drag").mousedown(function(e) {
                dragging = true;
                iX = e.clientX - this.offsetLeft;
                iY = e.clientY - this.offsetTop;
                this.setCapture && this.setCapture();
                return false;
            });
            document.onmousemove = function(e) {
                if (dragging) {
                var e = e || window.event;
                var oX = e.clientX - iX;
                var oY = e.clientY - iY;
                $("#drag").css({"left":oX + "px", "top":oY + "px"});
                return false;
                }
            };
            $(document).mouseup(function(e) {
                dragging = false;
                $("#drag")[0].releaseCapture();
                e.cancelBubble = true;
            })

        })

    </script>
</head>

<body>
    <div id="drag">
        <h2>来拖动我啊</h2>
    </div>
</body>
</html>
